1. Field of the Invention
The present invention relates to a display apparatus, an information processing apparatus capable of communicating with the display apparatus, and methods of controlling the display apparatus and information processing apparatus.
2. Description of the Related Art
A display apparatus typified by a digital television has a variety of external interfaces and is capable of data communication with various peripheral devices. Typical examples of such peripheral devices are digital cameras, video cameras, printers and remote controllers.
There is a display apparatus which, in order to display a GUI such as settings menu or electronic program guide, is equipped with a function for parsing markup language (HTML, XML, BML, SVG, etc.) and rendering text, graphics and images. To achieve this, a peripheral device capable of communicating with the display apparatus supplies the display apparatus with GUI data described in markup language, and the display apparatus renders the GUI data to present a display on its screen. Before this technique was available, a GUI generated by a peripheral device was rendered by the device, the rendered GUI data was supplied to a display apparatus as an image signal and displayed by the display apparatus. In other words, the display apparatus merely displayed an image signal and did not execute processing such as the rendering of GUI data.
However, since it has become possible for a display apparatus to render GUI data, it is now possible to present a display that is based upon the image quality, size and aspect ratio, etc., of the display apparatus. For example, by connecting a digital camera to the display apparatus as a peripheral device, supplying display data for rendering the GUI of the digital camera to the display apparatus and causing the apparatus to render this display data, it is possible for a user to perform camera settings, etc., while viewing GUI, which is based on optimized GUI data, displayed on the display apparatus.
However, processing for rendering markup language supplied from a peripheral device increases the processing load on the display apparatus. Consequently, if the display apparatus is under a heavy processing load owing to other processing, it can take time to obtain the result of rendering process of the markup language provided by the peripheral device. For example, if, in a case where the menu screen of a digital camera is displayed on the display apparatus and a menu operation is performed, it takes a prolonged period of time to obtain the result of rendering the menu screen, response to the menu-screen operation declines and operability suffers.
A known method of alleviating the processing load on a certain device in a system to which a plurality of devices are connected is to have some of the processing of the device under the heavy processing load be executed by another device whose processing load is light, as described in the specification of Japanese Patent Laid-Open No. 2003-029940, by way of example.
However, the peripheral device of a display apparatus often has a processing capability inferior to that of the display apparatus, and there are cases where the device is battery-driven, as in the case of a digital camera or remote controller. Accordingly, utilizing the device as one that executes some of the processing of the display apparatus is not advisable.
A further known method of alleviating processing load is to reduce the amount of processing or lower the complexity of processing if the processing load is heavy, as described in the specification of Japanese Patent Laid-Open No. 2006-261955, by way of example. In a case where the display apparatus executes such processing, however, if the processing load is heavy, the result of rendering process may be different from that expected on the side of the peripheral device. For example, the processing for rendering markup language may become too simplistic.